This invention relates to cleaning material from a suppprt surface, such as an imaging surface of a photocopier. More particularly the invention relates to methods and apparatus in which a cleaning blade engages a surface to be cleaned and the surface is driven past the blade.
To facilitate a clear understanding of the invention it is to be understood that the expressions "upstream" and "downstream" used herein and in the claims have the following meanings. The expression "upstream" refers to that direction from which any point on a movable surface travels. The expression "downstream" refers to that direction towards which any point on a movable surface travels. A cleaning blade may be disposed normally to the surface to be cleaned or it may be tilted in leading or trailing relation to the direction of movement of the surface. Such tilted blades are generally referred to respectively as scraper and wiper blades. These expressions as used herein and in the claims are defined as follows. A "scraper blade" is one which extends towards the surface in the upstream direction and when pressed against the surface exerts a chiselling action on material on the surface. A "wiper blade" is one which extends toward the surface in the downstream direction.
It has been found desirable, for example, in the case of a plastics blade acting on a photosensitive surface to remove residual liquid developer therefrom, in the environment of a xerographic copier, to separate the blade from the surface during shut-down periods, as between copy cycles, to avoid cold flow resulting in deformation of one or both of the blade and the surface. When the blade is removed from the surface, particularly in the case of liquid, material which has piled up against the blade will tend to spread out beyond the blade position when the support from the blade is removed. In an effort to alleviate this problem it is proposed in U.S. Pat. No. 3,940,282 to Hwa, that before each shut-down period, the relative motion between the blade and the surface is reversed prior to removing the blade from the surface. Such reversal of relative motion tends to break up and remove the build-up of material.